In Micro Electro Mechanical Systems (MEMS) devices, mechanical and electronic components may be combined to form miniature electronic devices in sealed cavities. Although MEMS devices may take a variety of forms to perform various functions, in general, the cavities which are part of MEMS devices need to be sealed with a particular pressure, such as a sub-atmospheric pressure, to suit the needs of a particular application. Sealing the cavity of a MEMS device at a particular pressure provides the MEMS device with a desired operating pressure, which is designed to be impervious to changes in pressure that may be experienced by unsealed portions of the semiconductor die within which the MEMS device resides.
One commonly utilized technique for forming a sealed MEMS cavity involves a process in which a MEMS cavity is sealed and shut using a sealing layer. However, utilizing a sealing material to seal a MEMS cavity may require various physical and chemical processes that may result in emission of gases from the sealing material into the MEMS cavity. For example, moisture may react with the sealing material to form bubbles in the sealing layer and outgas into the MEMS cavity. Also, some semiconductor wafers may undergo high thermal budget processes after the formation of the sealing layer, which can cause deformation of the sealing material and emission of gases into the MEMS cavity.
The emission of gases from the sealing layer into the MEMS cavity undesirably alters the operating pressure inside of the MEMS cavity, and also contaminates and damages mechanical or electronic components inside the MEMS device, thereby impairing device performance.